The present invention relates to an optical sensor unit and an image-forming apparatus.
Conventionally, image-forming apparatuses that perform image quality adjustment control such as process control, based on predetermined conditions such that immediately after the power is turned on, accumulation of printouts reaches a predetermined number, and so on are known. For example, the image quality adjustment control is performed as follows. Firstly, light emitted from a light-emitting element of an optical sensor unit as a light-emitting device is reflected by a surface skin part (a part where toner does not adhere.) of an intermediate transfer belt as an object to be detected, and the reflected light is received by a light-receiving element of the optical sensor unit as a light-receiving device, and an output signal (voltage) according to the reflected light is outputted. Next, a reference toner image that has a predetermined shape is formed on a surface of a photoreceptor, the reference toner image is transferred on the intermediate transfer belt, light emitted from the light-emitting element is reflected on the reference toner image as an object to be detected, the reflected light is received by the light-receiving element, and an output signal according to the reflected light is outputted. And then, the output signal on the surface skin part of the intermediate transfer belt is taken as a reference value, the reference value and the output signal in the reference toner image are compared, and a toner adhesion amount per unit area of the reference toner image is obtained. Based on the toner adhesion amount obtained in this way, image-forming conditions such as a uniform charge potential of the receptor, developing bias, optical writing intensity to the receptor, a control target value of toner density of a developer, and so on are adjusted such that the toner adhesion amount is a desired amount.
By such image quality adjustment control, it is possible to perform printout with stable image density for long periods.
There is a case where light other than the reflected light of the object to be detected such as the intermediate transfer belt, the reference toner image on the intermediate transfer belt, or the like enters the light-receiving element of the optical sensor unit. An output signal from the light-receiving element due to the light other than the reflected light of the object to be detected is called crosstalk (a crosstalk voltage, in a case where the output signal is voltage), and it is preferable to keep it as low as possible, because of degrading detection accuracy of the object to be detected.
Japanese Patent Application Publication number 2011-048185 discloses an optical sensor unit such that an output value of a light-receiving device when receiving light reflected from an object to be detected is corrected so that the output value in which a component of crosstalk is removed is obtained. Specifically, a shutter member that covers an incident/exit plane where an exit part where light of the optical sensor unit is emitted and an incident part where reflected light enters is provided, and a light absorption member is provided on a facing surface of the shutter member facing the incident/exit plane. When measuring the crosstalk, in a state of facing the light absorption member provided on the shutter member to the incident/exit plane (in a state where the shutter member is closed), light is emitted to the light absorption member. The light emitted to the light absorption member does not reflect, and the reflected light is not received by the light-receiving device. Therefore, an output voltage of the light-receiving device obtained by emitting the light at this time is an output voltage by the light other than the reflected light of the object to be detected, and is known as so-called crosstalk. Thus, it is possible to measure crosstalk of the optical sensor unit.